Multiscale instrument indicating system



Feb. 5, 194e. 'H Q MORGAN 2,394,196

MULTISCLE INSTRUMENT' INDICATING SYSTEM f/HRRY 6. Mom/aw.

Avleb. s, 1,946, .l

H. c. MORGAN MULTISCA'LE INSTRUMENT INDICATING SYSTEM' s Smets-sheet 2 Filed July 9, 1943 f/E 201i y l MM5' Feb. 5, 1946. l H. c. MORGAN 2,394,195

MULTISCLE NSTRUMENT INDICATING S'YSTEM Filed July 9, 1943 f 5 Sheets-Sheet 3 .rif M21 .atented Feb. 5, 1946 UNITED STATES PATENT orifice MULTISCALE INSTRUMENT INDICATING SYSTEM Harry C. Morgan, Dayton, hio, assigner, by

mesne assignments, to Curtis Engineering Company, Inglewood, Calif., a copartnership consisting of William H. Curtis and Russell R.

Curtis Application July 9, 1943, Serial No. 493,986

13 Claims. (Cl. 177-351) vals, reading various gauges, instruments, etc..

With the advent of multi-motored equipment, as wall as with the increase in the number of additional accessories, the number of y instruments mounted on the panel has materially increased. As a result, the operators responsibility has increased proportionately. y

The present invention relates to means for sim- A plifying the operators task of observing performance, and to reducing the panel space required for registration of various necessary readings.

The present invention relates to apparatus which includesa plurality of translators which vary an electrical output, or signal. in accordance with the variation of the quantity being measured, such as speed. pressure, temperature or other functional operation being quantitatively measured, and an interpreter for interpreting and registering the electrical response of each individual translator in a confined locality where it can bev observed by the operator. More particularly, it relates to a single indicating instrument and its associated apparatus and circuit, which instrument is provided with a multiplicity 'of scales which serve to provide a multiplicity of indications corresponding with a like number of conditions being registered.

The present invention is an improvement over my copending application entitled Multiplescale, multiple function instrument indicatingi system, U. S. Serial No. 486,410, led May 10, 1943, wherein the broad aspects of such a system are described and claimed.

It is an object of the present invention to provide a, novel multiple scale instrument indicating system.

It is a further object of the present invention to provide a novel method and means for connecting the interpreters to the translator.

Another object of the present invention is to;

ing a separate source oi low frequency different from one another, which are transmitted over a common channel to a receiving point where they are separated and `fed to the interpreter.

A still further object of the present invention is to provide a, multiple-scale instrument indicating system wherein the indications from the plurality of translators -are transmitted by a high frequency carrier to a receiving point where they are separated and applied to the interpreter means.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization, manner of construction and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a schematic wiring diagram illustrating a portion of a multi-scale instrument indicating system which includes the interpreter and the means for energizing the same;

Figure 2 is a schematic wiring diagram of a portion of a multi-scale instrument indicating system which includes a plurality of translators, the receiving means for segregating the various indications fromthe various translators, and the interpreter; and

Figure 3 is a schematic diagram of a modiiied form of the present invention wherein the various indicators from the translator are transmitted by a high frequency carrier to the interpreter.

In Figure 1 of the drawings there is diagrammatically illustrated the principal component parts of the interpreter and the energizing circuit therefor, of a multi-scale instrument indiand claimed in my copending application Serial No. 486,410 hereinbefore referred to. This cathode ray tube III is provided with a cathode II which is indirectly heated by a filament I2. Adjacent the cathode II is a control grid I3 which is adapted to regulate the number of electrons in the sheet drawn from the cathode I I. This control grid |3 is provided with a suitable negative biasing potential through a conductor` I4. Next to the control grid I3 is an accelerating anode I 5 which is provided with a sufliciently high positive biasing potential through conductor I8 to cause a sheet o! electrons to be drawn from the cathode II.

Disposed beyond the accelerating anode I5 is a focusing electrode I1 which is provided with a positive bias through conductor I8. This iocusg ing electrode I1 is arranged in such a manner that'the line formed, when the electron beam strikes the fluorescent screen I9 in the enlarged end of the tube I9, will be focused to the desired width. A second accelerating anode is disposed adjacent the focusing electrode I1 and receives its biasing potential through conductor 2|.

Disposed beyond the second accelerating electrode 20 is a deector platev 22 and a plurality of deilector plates 23, 24, 26 and 26. The deector plates 23 to 26 in conjunction with the deector plate 22, are arranged to deflect segments o! the sheet or electrons in response to changes in the electric biasing potentials applied to them. A Faraday electrostatic screen 21 is provided to isolate the various deiiector plates 22 to 26 from one another. Deector plate 22 is connected to ground through conductor 28 as well as to conductor 2l from second accelerating anode 20' which is also grounded. Deiiector plates 22 to 26 receive their variable biasing potentials through conductors 29 to 32 respectively in a manner-presently to be described.

From the above description it will be apparent to those skilled in the art that any one of the deector plates 23 to 26 can cause a portion or segment of the sheet of electrons passing between the deflecting plates 23 to 26 and the deilector plate 22, to be deflected, thereby causing that segmental portion of the sheet of electrons to strike the fluorescent screen I9 at a different.

point therealong. It will thus be apparent that while only a single cathode ray tube is employed, and that while only a single electron emitting source is provided; nevertheless, a plurality of indications is obtained simultaneously on the iluorescent screen I9 along suitable scales 33 to 36, depending upon the respective biasing potentials impressed on the various' deiiector plates 22 to 26. This enables a multi-scale, multi-function instrument to be provided with a single cathode ray tube having a single electron emitting source.

The necessary biasing potential for the cathode ray tube II) is obtained from a full wave rectiiier comprising a transformer 31 having a primary winding 38 arranged to be connected to a suitable source of alternating currentthrough conductors 39 and 40. The transformer 31 is provided with a filament heating winding 4I which is connected through conductors 42 and 43 to filament l2 of the cathode ray tube I9. Secondary windings 44 and 45 in conjunction with a rectiiier tube 46 provide a conventional full wave rectiiier i'or supplying high voltage direct current to the cathode ray tube I 0. The output circuit of the full wave rectier includes conductors 41 and 46. Conductor 41 is connected to one end of a voltage divider potentiometer 49 and conductor 48 is connected through a choke 50 and a rheostat 5I to the other end of the voltage divider potentiometer 49. A pair of filter condensers 52 and 53 are provided in the output circuit.

The voltage divider potentiometer 49 is so designed and arranged that with all measured apparatus shut oil, all indicating lines on the iluoressent screen I9 of the cathode ray tube I0 can be adjusted to the zero point at one end of each o1' the scales 33 to `36. The deilector plates 28 to 26 are each connected by their associated conascenso ductors 29 to 32 respectively through isolating resistors 54 to 51 respectively and common conductor 58` to the movable contact 59 on the voltage divider potentiometer 49. These isolating resistors 54 to 51 are of relatively high ohmic value, such, for example, as one million ohms each. These isolating resistors are arranged to prevent changing potentials in one of the deiiector plates 22 to 26 from influencing the remaining deflector plates of that group. The voltage divider potentiometer is also provided with movable contacts 60: 6I, 82, 63, and 64. A movable contact 60 is connected through conductor I4 to the control grid I3. Movable contact 6I is connected through a conductor' 65' to cathode II. Movable contact 62 is connected through conductor I6 to therst accelerating anode I5. Movable contact 63 sconnected through conductor I8 to the focusing electrode I'l. Movable contact 64 is connected through a conductor 66 The left to the Faraday electrostatic screen 21. hand end of the voltage divider potentiometer 49 is connected through a conductor 61 to conductors 2I and 28 which in turn are connected to the second accelerating anode 28 and deflector plate 22 respectively. This conductor 61 is also grounded as shown. 1

'Ihe right hand portion of'Figure i illustrates how the various translators may be connected to the cathode ray tube Ill.,l The translators are diagrammatically indicated by the reference characters 68, 69, 10 and 1I. 'As will presently bedescribed in connection with Figures 2 and 3 of the drawings, the translators are arranged to apply an alternating current biasing potential proportional to the conditions being registered. 'I'he alternating current biasing potential for translator 68 is fed through a conductor 12 and a rectifier 13 to a pair of resistors 14 and 15 conv nected in series, the return circuit being through' ground as indicated. It will thus be apparent that a voltagedrop occurs across the resistors 14 and 15 which is proportional to the output voltage o! the translator 68. The midpoint between resistors 14 and 15 is connected through a conductor 16 and conductor 29 to deiiector plate 23. The output of translator 69 is similarly connected through a rectiiier 11 to two series connected resistors 18 and 19, the midpoint of which is connected through conductor and conductor 30 to deiiector plate 24 of the cathode ray tube Ill.v

The output of translators 10 and 1I are similarly connected to rectiliers 8I and 82 to a pair of resistors 83 and 94 and a second pair of resistors 85 and 86 respectively in the manner shown. The midpoint between resistors 83 and 84 is connected through a conductor 81 and conductor 3I to deflector plate 25, while the midpoint between resistors 85 and 86 is connected through aconductor 88 and conductor 32 to deilector plate 26 of the cathode ray tube I0.

Filter condensers 89 to 92 are preferably provided in the output circuit of each of the translators 68 to 1I respectively to keep all alternating current out of the resistors 14,l 15, 18, 19, 83, 84, 85 and 86.

From the above description it will beunderstood that the respective positions of the various segmental portions oi the sheet or electrons striking the fluorescent screen I9 andthejcathde ray tube I8 depend lupon the particular lb d g voltage applied on the deilector plates t2.3 to 26. fThe particular segmental portions of the sheet of electrons associated with each of the scales 33 to 36 are indicated by the reference characters 93, 94,

assenso 95 and 90 respectively, I'he relative position of each of these segmental portions of the sheet oi' electrons will change as the biasing potential on the deflector plates 23 to 26 change in response to changes in the value of the conditions being measured by the translators 38, 69, 10 and 1|.

In Figure 2 of the drawings there is illustrated a system in which a plurality of different low frequency oscillations, one associated with each condition to be measured, are provided. The amplitude of the low frequency oscillation varies in response to the condition to be measuredy and all indications are fed over a single pair of transmitting conductors to the locality of the interpreter where the low frequency oscillations are segregated and rectified. The rectied output of each segregated low-frequency oscillation is supplied to one of the defiector plates of the cathode ray tube i which has been described in detail in connection with Figure i.

Referring now to the specific apparatus shown, four resistors, 91, 38, 90 and |00, each of which has an associated movable contact |0i, |02, |03 and |00 respectively are arranged to be actuated by movable elements |05, |00, |01 and |00 respectively, the movement of which is responsive is not shown but it is to be understoodthat the conductor i I3.

filament of each of the triodes IIB to iilis heated in a conventional manner. 'Resistors |38, |31, and |30'are connected across nlaments |20, |23, |23, and |23 respectively. The midpoint of each of these resistors to |33 are connected through self biasing resistors |40, |4I, |42 and |43 to thegrounded transmission :BY-D886 condensers |44, |45, |43 and |41 are connected across resistors |80 to |43 respectively. V

A resonant filter is provided in the output circuit of each of the triodes H0 to il@ so that the output circuit of one triode is tuned to a thousand cycles, a second vtriode yis tuned to two thousand cycles, a third to three thousand cycles and a fourth to four thousand cycles. resonant filters are diagrammatically illustrated by an inductance element and a condenser element'.` More particularly, the output circuit -of triode ilB is provided with a rnant filter in'- cluding an inductance element |00 and a condenser |49, the latter being connected in parallel to theintensity or amplitude of value of the condition being measured. Isolating resistors isolate the various resistors 91, 93, 09 and |00 from variations of position of each other. Resistor s1 is connected to some suitable source of low` frequency oscillation, such, for example,

as a one thousand cycle source, through conductor |00. Resistor 08 is connected, through conductor i0, to another source of low frequency Y oscillation having a diderent frequency than that to which resistor 01 is connected, such, for example, as a source having a two thousand cycle frequency. Resistor 90 is connected through conductor Iii to still another source of low frequency oscillation having a frequency, such, for example, as three thousand cycles per second. Resistor |00 is connected through conductor i l2 to a fourth source of low frequency oscillation, such, for example, as a source of four thousand cycles per second.

The lower end of each of the resistors 01 to |00 is grounded through a conductor M3. The movable contact elements |0| to |00 are each connected to a common conductor iid; through isolating resistors |00, 200, 20| and202; which in turn is connected to the transmitting conduc- I fed into the common transmission line comwith thev former. The output circuit of triode ||1 is provided with a reso i filter tuned to two thousand cycles which includes inductance element |50 and condenser |06. The output circuit of triode ||8 includes a .resonant filter tuned to three thousand cycles having an inductance element |52 and a condenser |53. The

output circuit of triode iiii is provided with a resonant filter tuned to four thousand cycles which includesan' inductance element 00 and a condenser |55. Positive big potential for the plates |22, |25, |28 and li of triodes H90 to M0.

is provided through conductor 00" which is connected to a suitablesourceof positive biasing potential '(it being understood that the low voltplate |20 through conductor its and inductance posed of conductors IIE and H3. In proximity to the cathode ray tube interpreter i0; which for punposes of simplicity is diagrammatically illustrated by showing the large deector plate 22 and the smaller confronting deflector plates 23 to 26; four triodes H6, ||1, H0 and-H9 are provided. The vacuum tube triode ||6 includes a filament |20, a control grid |2| and a. plate |22. Triode |l1 includes a filament |23, a control grid |24 and a plate |25. Triode ||8 includes a filament |25, a control grid |21 .and a plate |28. Triode H9 includes a filament |29, a' control grid |30 and a plate |3|.

Transmission line conductor ||5 is connected to control grids |2|, |24, |21 and |30 through isolating resistors |32, |33, |34 and |35 respectively. The lanient heating current supplied |50. Plates |20 and |3| similarly receive theirpositive biasing potential through conductor |50 and inductances it-and itrespectively.

One thousand cycle current is fed by resonant filter |40, its through a coupling condenser |57 to rectifier |50. This rectifier |50 is diagrammatically illustrated as being of the dry disk type but may, of course, be of any suitable variety which will rectify the low frequency current impressed thereon. The rectified current which passes through rectifier |58 to load resistors 10 and 15 has previously been described in connection with Figure 1. The midpoint between resistors Hand 13 is connected through conductor 16 to deilector plate 23 of the cathode ray tube |0. It will thus be apparent that the magnitude of the biasing potential on deflector plate 23 will be directed proportional to the amplitude of the voltage wave of the thousandA cycle low frequency oscillation transmitted over conductors ||5 and 3.

'Ihe two thousand cycle resonant filter |50, |5| is connected through a coupling condenser |59 to arectifier |60, preferably of the dry disk type. The rectified current passing through rectier |00 is fed through load resistors 18 and 19 to ground, through conductor |6|. The midpoint betwe'en resistors 18 and 13 is connected through conductor 00 to deector plate 24 which has previously been described in connection with Fig- .ure 1.- It will thus be apparent that. the biasing potential on deector plate 24 will be propor- These tional to the amplitudeof the voltage wave of the two thousand cycle current transmitted over conductors ||8 and IIS. Y

Resonant lter |52, |88 is connected through a coupling condenser |82 to a' rectier |88. 'I'he rectified current passing through rectifier |88 is fed through load resistors 88 and 84 to the grounded return conductor |8|. The midpoint between resistors 88 and 84 is connected through conductor 81 to a deilector plate 28 as has been described in connection with Figure 1.- It will thus be apparent that the magnitude of ing potential on the deector plate 28 will be proportional to the amplitude of the voltage wave of the three thousand .cycle current suppliedA through transmitting conductors ||8 and H8.

Resonant filter |84, |88 is connected through a coupling condenser |88 to a rectifier |88. The rectified current passing through rectiner |88 is fed through load resistors 88 and 88 to the grounded return conductor |8|. The midpoint between resistors 88 and 88 is connected through conductor 88 to deflector plate 28 as has been described in connection with Figure 1. It will thus be apparent that the magnitude of the biasing potential on deflector plate 28 is proportional to the amplitude of the voltage wave of the four thousand cycle current supplied through conductors ||5 and H8.

It will be further apparent that all of the indicating signals from the various translators. Iare fed through a single pair of conductors. Due

to the filter networks and due to the fact that a different low frequency is associated with each translator, it will be apparent that variations in the amplitude of the voltage wavefrom one translator will not interfere with the transmission of the biasconductor |81.

connected through resistors'ir-to |88 respectively. which in turn are all connected to a single Thus the voltages taken from the various voltage dividers |88 to |88 are all impressed on the grid |88 of a modulator tube |88 of a radio transmitter |88. 'I'he modulator tube is illustrated, for purposes, of simplicity. as a triode having an anode |8|, a control grid |88 and a signals from the other translators, even though they all be fed into a single pair of transmission Y conductors I8 and H3.

In Figure 3 of the drawingsa modiiied form of the invention isY diagrammatically illustrated. More particularly, Figure 3 shows an arrangement in .which the various low frequency currents coming from the different translators modulate la.

high frequency carrier wave which is then transmitted to a radio frequency receiving station where the modulated carrier wave is received, demodulated. filtered, rectied and fed to the interpreter tube. More particularly, the system shown in Figure 3 includes four potentiometers or voltage dividers |88, |81, |88 and |88. These potentiometers are connected to different sources of low frequency alternating current. For example, potentiometer |88 is connected through conductor |18 to a source of one thousand cycle alternating current. Potentiometer |81 is connected through conductor |1| to a source of two thousand cycle alternating current. Potentiometer |88 is connected through conductor |12 to a three thousand cycle source of alternating current. Potentiometer |89 is connected through conductor |13 to a four thousand cycle source of alternating current. Each potentiometer or voltage divider element |88 to |88 is provided with a movable contact element |14 to |11 respectively, which rmovable contact elements are moved by an associated mechanism diagrammatically illustrated by the rods |18 to |8| respectively. It is to be understood that these rods |18 to |8| are arranged to be moved amounts proportional to the condition being measured.

lament |82. A biasing resistor |88 is provided v.between the grid |88 and the filament |82. The

lament heating circuit is not shown but it will be understood that this may be of any conventional design. The output of the radio transmitter is fed to' an antenna which is diagrammatically illustrated at |88.

A radio receiver |98 is provided which is connected to a receiving antenna |88 to pick up the signals transmitted from the antenna |88. This receiver may be of any.l conventional design with radio frequency amplification and automatic volume control. The output of the radio frequency amplifier is fed to a detector or demodulator |81. The output of the demodulator |81 is thus a complex wave which is a combination of the four low frequency waves sent out from the four translators. The output of the demodulator |91 is fed to a group of resonant filters and rectiers as diagrammatically illustrated at |88. These may be generally of the type which has previously been described in connection with Figure 2 of the drawings. The output from the various resonant filters |88 are fed to lassociated ciflector plates 28 to 28 of the interpreter tube In connection with this system it will be understood that the magnitude of the carrier wave is' the full scale deection magnitude reference.

The percentage of'modulation of the thousand cycle, two thousand cycle, three thousand'cycle and four thousand cycle current applied to the carrier determines the amount of deflection on the fluorescent screen of the cathode ray tube I8.

The resistors |88 to |88 which are connected between the voltage divider elements |88 to |88 in the grid |88 are isolating resistors and serve to prevent interferencebetween the various translators.

While I have'shown particular embodiments of my invention, it will, of course, be understood that I do not wish to be limited thereto, since many modiiications'maybe made, and I thereforecontemplate, by the appended claims, to cover all such modifications as fall within the true spirit and scope of my invention.

VI claim as my invention:

1. A multi-scale instrument indicating system comprising a plurality of condition determining devices, each having means for supplying a different predetermined low frequency oscillation and only one -of said low frequency oscillations being associated with each of said condition determining devices, means for changing the condition of each of said low frequency oscillations as a function of the condition being measured, a. single cathode ray tube having a plurality of scales on a fluorescent screen contained therein, means for producing a single stream of electrons within said tube which impinge on the scale portions of said screen and which electrons are arranged to excite a local area on each scale portion, and means for independently varying the position where said electrons impinge on each scale portion as a function of the modified low frequency oscillations.

2.'A multi-scale instrument indicating system y, dition deter comprising at least three condition determining devices, each having means for supplying alow frequency oscillation' of a frequency -diilerent than that of the remaining ones and only one of said low frequency oscillations being associated single cathode ray tube having a plurality ofscales on a fluorescent screen contained therein,

means for producing a single stream of electrons within said tube which impinge on the scale por-l tions of said screen and which electrons are ar ranged to excite a local area on each scale portion, and continuously excited means for varyingthe position where said electrons impinge on each scale portion as a function of theintensity of said low frequency oscillations and independently of each other, each of said low frequency oscillations having a different scale associated therewith.

3. A multi-scale instrument indicating system comprising a plurality of condition determining devices, each having means for supplying a different predetermined low frequency oscillation and only one ofl said low frequency oscillations being associated with each of said condition determining devices, means for changing the condition of each of said low frequency oscillations as a function of the condition being measured,` ya radio transmitterincluding means for transmitting a high frequency carrienmeans for modulating said carrier with all of said low frequency oscillations, means'for receiving and demodulating said complex modulated carrier, lter means for segregating the demodulated low frequency tional to the amplitude of the-rectified outputs of said received oscillation. whereby the position of Aeach segmentall portion where it strikes said screen is a function of itsl associated condition determining device. i

5. A multi-scale instrument indicating system comprising a plurality of condition determining devices, a corresponding-number of translators,

' each of said translators'including means for supplying a different identifying low frequency signal, the intensity of which is proportional solely oscillations, means for rectifying said demodulated low frequency oscillations, a single cathode `ray tube having a fluorescent screen with a plurality of scale portions thereon, one for each consingle stream of electrons which impinge on a local area .of said scale portions ofsaid screen. and form an indicating indicia, a plurality of electron stream deecting means within said tube.

for varying the place where the electrons impinge on each scale portion, there being a separate means for each scale, each of said means being continuously energizedv and varied independ-v ently as a function of a different one of said rectiiied demodulated low frequency oscillations.

4. A multi-scale instrument indicating system comprising a plurality of condition determining devices, each having means for supplying a different predetermined low frequency oscillation and only one ofvsaid low frequency oscillations being associated with each of said condition determining devices, the amplitude of which is a function of the condition being measured, -a receiving station, means for transmitting said oscillation by a common carrier to said receiving station, said receiving station including means for ning device, means for producing a to the value of the condition being determined by its single associated condition determining device, a single cathode ray tube indicator having a fluorescent screen with a plurality of indicating scale portions, Aone for each translator, said tube having means for projecting a stream of electrons against said screen and arranged to locally excite a portion of said screen portions, means for independently defiecting the electrons striking each scale portion therealong as a function of the intensity of each of said scales associated low frequency oscillation.

6. A multi-scale instrument indicating system comprising a plurality of condition determining devices, a corresponding number of translators, each of said translators including means for supplying a different identifying low frequency signal, the intensity of which is proportional solely to the value of the condition being determined by its single associated condition determining device, a single cathode ray tube indicatorhaving a fluorescent screen with aplurality of indicating scale portions, one for each translator, said tube having means for projecting a stream of electrons against said screen and arranged to locally excite a portion of each of said scale portions, means for feeding all of said low frequency signals through al single common channel, means for receiving and segregating the low frequency signals so fed through said common channel, separate means independently of each other for deecting the electrons striking each scale portion therealong, and means for energizing each of said separate deflecting means as a function of one of said received low frequency signals.

7. A multi-scale instrument indicating system comprising a plurality ofl condition determining devices, a corresponding number of translators, a single interpreter having a plurality of indicate ing scales and anr indicating means associated with each scale to'register the value of the condition being determined, each of said translators having means for supplying a single identifying signal different from all other identifying signals, the intensity of which is a function of the condition being measured, and means for moving each of said indicating means as a function of the intensity of its associated identifying signal, each moving means being unaffected by the condition of all the other moving means.

8. A multi-'scale instrument indicating system including a plurality of translators, a single interpreter having a plurality of indicating scales, and an indicating means associated with each scale, each of said translators having means for supplying a single identifying low frequency signal dierent'from all other identifying signals whose intensity is arranged to vary, and means for independently movingeach of said indicating means as a function of the intensity of its associated low frequency signal.

9. A multi-scale instrument indicating system including a plurality of translators, a single infor moving each each other as a function of thek means for feeding each of said low frequency signais through one of said isolating resistors to and over said pair of conductors, filter means for segregating said low frequency signals transmitted over said pair of conductors, and means of said indicating means independently of intensity of a different one of said received low frequency signals.

10. A multi-scale instrument indicating system including 'a plurality of translators, a single interpreter having a plurality of indicating scales. and an indicating means associated with each scale, each of said translators having means for supplying a different identifying low frequency signal whose intensity is arranged to vary. a pair of conductors, a plurality of isolating resistors, means for feeding each of said low frequency signals through one of said isolating resistors to and over said pair of conductors, filter means for segregating said low frequency signals transmitted over said pair of conductors, means for rectifying each of the segregated received low frequency signals, and means for denecting each of said indicating means as an independent function of the intensity of its associated rectified low frequency signal.

.11. A translating circuit for a multiple scale instrument indicating system comprising a plurality of sources of alternating current, each source having a different frequency, the voltage of which is a function of a condition to be indicated, means for mixing said alternating currents and sending them over a common channel. a plurality of vacuum tubes, each having a cathode, an anode and a control electrode, means connecting said common channel across the control electrode and the cathode of each tube, means for giving the anode of each tube a positive bias, a illter network connected in the output circuit of each tube. each lter network being arranged to pass a different one of said frequencies, and means for applying the potential of each alternating current passed by each of said nlters to an indicating instrument.

12. A translating circuit for a cathode ray tube indicating instrument of the type having a plurality of control electrodes electrostatically shielded from each other comprising a plurality of sources of alternating current energy, each source having a different characteristic frequency, the voltage of which is a function of a asocian' y condition to be indicated. means for transmitting said different energy waves simultaneously over a common channel. a pluralityof electron discharge devices each having a cathode. an anode and a control electrode, means connecting said common channel across the control electrode and the cathode of each of said electron discharge devices, means for impressing a positive biasing potential on each anode. means for segregating a diiferent one of the characteristic frequencies in the output circuit of each electron discharge device, the output of each of said segregating means being thus arranged to pass a diiferent one of said characteristic frequencies, and means for applying the potential of each of the different characteristic frequency waves to separate one of said control electrodes of said'cathode ray tube.

13. A translating circuit for a cathode ray tube indicating instrument of the type having a plurality of control electrodes electrostatically shielded from each other comprising a plurality of'sources of alternating current energy.;eah source having a different characteristic frequency, the voltage of which'is a function of a condition to be indicated, means for transmitting said different energy Waves simultaneously over a common channel, a plurality of electron discharge devices each including an anode, a 'cathode 4and a control grid, a plurality oi.' resistance elements of relatively high ohmic value each connected at one end to a different one of said control grids and at the other end to one side of said common channel, each cathode having a se1f-' biasing resistor and capacitor connecting it to the other side of said common channel and ground, a plurality of parallel resonant lter networks including an inductance element and e.v

capacity element connected in parallel. one side of each of said parallel resonant'networks being connected to a different one of said anodes and the other .side being connected to a common source of anode biasing potential, each lter netv work being tuned to a diiferent one ofsaid characteristic frequencies, a resistance load for each characteristic frequency, reactifying means connectlng each filter network to said resistance load, and means for deriving a biasing potential from each resistance' load for a different one of said control electrodes of said cathode ray tube whereby the different biasing potentials on the different control electrodes of said cathode ray tube are independently a function of the relative values of the different characteristic alternating potentials of said sources.

HARRY C. MORGAN. 

